Microprocessor

ABSTRACT

The invention relates to a microprocessor having a plurality of components which are selected from registers ( 14,16 ), arithmetic logic units ( 30,32 ), memory ( 36,38 ), input/output circuits and other similar components where the plurality of components are interconnected in a manner which allows connection between some of the components to be varied under program control.

FIELD OF THE INVENTION

This invention relates to a microprocessor and relates particularly,though not exclusively, to a microprocessor which can have aprogrammable instruction set.

BACKGROUND OF THE INVENTION

Typical microprocessors have registers, arithmetic logic units, memory,input/output circuits and other similar components which are hard wiredtogether. The techniques for fabrication of such microprocessors is wellestablished and provides a cheap and powerful base for modern computers.In order to add three numbers together from memory and return the resultto memory, the traditional method is as follows:—

1. Memory→Reg A (Read from memory and output to register A)2. Memory→Reg B (Read from memory and output to register B)3. Reg A+Reg B→Reg C (Add registers A,B and output to register C)4. Reg C→Reg A (Read register C and output to register A)5. Memory→Reg B (Read from memory and output to register B)6. Reg A+Reg B→Reg C (Add registers A,B and output to register C)7. Reg C→Memory (Read register C and output to memory)

From the above it is clear that such a simple operation would take atleast 7 clock cycles to be completed. In addition, the presentmicroprocessor architectures are slow, because programmers are forced touse an instruction set provided by the microprocessor manufacturer. Thusthe programmer must construct their own software to use these set ofpredefined instructions. This example is grossly simplified as basicmicroprocessors do not take one cycle to process an instruction.Typically there would be a clock cycle for each of fetching theinstruction, loading an opcode into the instruction register anddecoding the instruction and processing the opcode per se.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide a microprocessorwhich is not limited to the instruction set provided by themanufacturer.

A further object of the invention is to provide a microprocessor withcomponents that can be interconnected in a variable manner.

Yet another object of the invention is to provide a microprocessor thatis more flexible in its operation than conventional microprocessors.

SUMMARY OF THE INVENTION

With these and other objects in view the present invention provides amicroprocessor having a plurality of components which are selected fromregisters, arithmetic logic units, memory, input/output circuits andother similar components commonly found in microprocessors, whereby saidplurality of components are interconnected in a manner which allowsconnection between some of the components to be varied under programcontrol.

Preferably said plurality of components are interconnected on a gridwhereby each of said plurality of components can be switched underprogram control to be connected to a predetermined selection of one ormore of said plurality of components.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood and put intopractical effect, reference will now be made to the accompanyingdrawings, in which:—

FIG. 1 is a block diagram of an embodiment of a microprocessor made inaccordance with the invention;

FIG. 2 is a similar view to that of FIG. 1 showing the interconnectionof components;

FIG. 3 is diagram to illustrate the loading procedures for a computerwhich includes the microprocessor of the present invention;

FIG. 4 is block diagram showing the microprocessor in one mode ofoperation;

FIG. 5 is a view of the interconnections to link various components ofthe microprocessor shown in FIG. 1;

FIG. 6 is a similar view to that of FIG. 5 showing a first embodiment ofproviding the interconnections;

FIG. 7 is a similar view to that of FIG. 5 showing a second embodimentof providing the interconnections;

FIG. 8 is a similar view to that of FIG. 1 showing a variation ofpositioning of components; and

FIG. 9 is a similar view to that of FIG. 8 showing a multi-gridarchitecture.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 of the drawings there is shown a microprocessor 10 whichincludes the following components:—

An internal clock 12 to provide the timing signals for operation of themicroprocessor. The internal clock 12 stores the time and date as wellas the clock which times when a new instruction should be read. Internalclock 12 can be programmed to accommodate longer instructions by varyingthe length of the clock cycle.

Registers 14-16 are basically intermediate storage devices used to storetemporary data. The microprocessor still relies on the registers toperform this task but allows the use of the register to be used more forstoring important and common data rather than an intermediate storagedevice in between its final destination. The registers store an N—bitword as well as some of the basic flags. Flags are reminders of whatoccurred in the last arithmetic logic units (ALU) 30-32 output results.Such flags are:—

Carry—if the last operation generated a carry from the most significantbitZero—if the result of the last operation was zeroOverflow—if the last operation produced a two's complement overflowSign—if the most significant bit of the result of the operation was 1.Parity—if the number of one bits in the result of the last operation waseven (even parity or odd (odd parity)Half-carry—if the last operation generated a carry from the lowerhalf-word

These flags are only stored for each associated register and theinstruction set decoder 34 must decide if the flags will have aninfluence on the next calculation. Registers 14-16 will also beconnected to the instruction set decoder 34 as will any flags associatedwith each register. Because more than one operation can occur at once weneed to store the associated flags for each register. The flagattachment to each register is ideal for a solution to the problem, thatmore than one operation will occur at once but this is only a suggestionand there are many ways of implementing flags in the microprocessorarchitecture. (This is unlike some traditional architecture which onlyhas one flag register)

ALUs 30-32 can Perform the Following Functions:—

-   -   1. Addition    -   2. Subtraction    -   3. Logical AND    -   4. Logical (Inclusive) OR    -   5. Logical Exclusive OR    -   6. Logical NOT (complement)    -   7. Increment (Add 1)    -   8. Decrement (subtract I)    -   9. Left shift (add input to itself)    -   10. Clear (Result is zero)    -   11. Multiply/Divide (May be a procedure or single command)    -   12. Compare functions such as greater than, less than and equal        to    -   13. Shift Data Left, Shift Data Right    -   14. Any other common or required function can be added to enable        microprocessor 10 to have access to these required functions.

The ALU 30-32 can change from a simple adder to a complex unit that canperform many arithmetic and logical functions. Therefore if the ALUcannot perform a function directly, several instructions will benecessary in order to produce the desired result.

Internal memory 36-38 can comprise cache, general purpose internalmemory, stacks, internal sound card, and other internal functions likevideo, modem etc.

External memory 40-42 can comprise cache, general purpose memory,internal sound card, and other internal functions like video, modem etc.Except unlike internal memory 36-38 external memory is not on themicroprocessor per se and the read and write speed is a lot slower thaninternal memory 36-38.

An internal instruction set 44 comprises a set of instructions which maybe a single command or a set of commands to comprise a procedure. Itcould even be capable of calling other basic instructions in aninstruction based procedure. There may be more than one internalinstruction set types like RAM for temporary and EEPROM for criticalinstructions (or critical procedures).

The instruction set decoder 34 interprets the instruction set into timedcontrol signals to the registers 14-28, ALUs 30-32, internal clock ofmicroprocessor 12, memories 36-44 and XY or grid connector 46 and/or anyother device to be controlled by the microprocessor.

Address registers 18-28 are basically registers that hold the current ornext address for a particular portion of memory. In traditionalmicroprocessors there is only one address register which limits you toread data sequentially. Whereas microprocessor 10 has a number ofaddress registers one for each main segment (or memory chip) of memory.This allows the microprocessor to read the data from one address andwrite it to another address assuming that there are two distinct memorysegments. Where a segment is a physically different memory, like memorychips or a hard-drive then every memory segment will have its ownaddress register.

XY connector 46 controls an X-Y grid which is formed of X bus lines50-62 and Y bus lines 64-78. Thus XY connector 46 will interconnect acomponent on the X bus e.g. ALU 30 to a component on the Y bus e.g.register 14. The interconnection can be made in various ways as shown inFIGS. 5 to 7. The basic interconnection is shown in FIG. 5 where eachintersection or node of a Y bus line with an X bus line containsswitches (not shown) which can be activated by a control register orsimilar under program control. To simplify the description only one busline is shown with a more complete description of the bus discussed withreference to FIGS. 6 and 7. The number of control bits in the controlregister to select the appropriate switch positions can be calculated asfollows:—

N=X·Y

Where N is the number of bits in the control register; X is the numberof X bus lines; and Y is the number of Y bus lines. Thus each bit willcontrol one associated switch. If required, the number of bits can bereduced by compressing the data because not all possible combinations ofswitching will be required.

FIG. 6 shows a second embodiment where a bi-directional switch 80 with asingle position. There is shown a bus of 4 wires for simplicity but thebus width can be any number i.e. B=1 to n, where B is the bus width andn is an integer. Using the 4 wire bus scheme there would need to be 4bi-directional rotary switches per each X unit or for each Y unit. FIG.6 shows ALU1 30 (a Y unit) connected to any X unit (Registers 14, 16A,16B, 16C) via the position of the rotary switch. The problem with thissolution is that there is only one possible switch location which limitsthe microprocessor architecture. This solution will however provide asimpler design to implement. A further option for the limiting to theone position is to have two switches so that the possibility of two ormore positions can be made available by adding another switch.

The third embodiment shown in FIG. 7 overcomes the problem by having abi-directional switch 82 with multiple positions. This is particularlyefficient and flexible method of implementation of switching. FIG. 7shows all the bus connections. This example also uses a 4-wire bus,where when one node is closed then all 4 switches associated with thatnode also close. FIG. 7 shows how the X bus is connected to the Y busvia 4 bi-directional switches. Therefore for a B size bus we wouldtherefore require B switches per node. For the example shown in FIG. 7there are 4 nodes, which can connect the ALU 30 to Registers 14, 16A,16B, 16C in any combination. All 4 nodes can be connected to Registers14, 16A, 16B, 16C, or some can be closed. Accordingly, there are 16possible combinations in this example for what nodes can be closed andopen.

The operation of microprocessor 10 is shown in FIG. 2. In this examplethe switch positions have been labelled as 86-96. The switch positions86-96 have been set by XY connector 46 in its control register. Thisresults in the following operations:—

External memory 42→External Memory 40→Register 16 (switches 94,96)Internal memory 36→Register 14 (switch 86)Register 16A→ALU 32 (switch 88)Register 16B→ALU 32 (switch 90)Output of ALU 32→Register 16C (switch 92)

This set of connections shows the potential for microprocessor 10 toperform multiple operations in a single clock cycle. Obviously only onedatum (word) can be output on to any data bus but multiple componentscan read the particular data bus. For example, where the external memory42 is stored into external memory 40, it can also be stored intoregister 16 as seen above.

From the above it can be clearly seen that a bad programmer could easilycause a bus crash. Accordingly, there must be software and hardwareerror checking Hardware error handling is performed by reading theinstruction set before it is performed, or while it is in the process ofbeing performed. This is achieved by reading the instruction set andperforming a simple check to see that no two components are output ontothe same data bus. When an error occurs the software is halted and afatal error message is returned. This method of error handling isbasically a back up if the software error handling does not work. Forsoftware error handling a preferred method is to put checks into thesoftware so that before the software compiles its programs, it performsa check to see if the instruction set will perform a fatal error.Therefore the error can be fixed before it occurs by the softwaredeveloper. Again this has limitations because it is very difficult topredict some outcomes of complex software.

In the description of the prior art an example was given which showed atraditional method of operation for adding three numbers together frommemory. The example took at least 7 clock cycles. The same example willnow be shown with reference to microprocessor 10.

1. Memory 36→Register 14 2. Memory 36→Register 16A 3. Register14+Register 16A→Register 16B, Memory 36→Register 16C 4. Register16B+Register 16C→Memory 36

Such a sequence of operations takes 4 clock cycles and results in a 175%increase in speed from the traditional method. Again with reference tothe prior art example microprocessor 10 can perform a single operationin one clock cycle or it the instruction set memory could be programmedto perform a whole operation which could comprise a number ofsub-commands. You could also write a program just in simple instructionsa clock cycle at a time, rather than an instruction which takes around 4clock cycles in the prior art. This would allow an instructioncontaining several clock cycles with no definite length.

If the numbers in steps 1 and 2 above are from different memories thentwo buses can be used to download both numbers to two registers in onecycle as shown in the following example:—

1. Memory 36→Register 14, Memory 40→Register 16A 2. Register 14+Register16A→Register 16B, Memory 36→Register 16C 3. Register 16B+Register16C→Memory 36

This will provide a 233% increase in speed from the traditional method.

If the ALUs 30, 31, 32 can be timed and operate quick enough to be ableto be operated in cascade, then a further increase in speed can beobtained as follows:—

1. Memory 36→Register 14, Memory 40→Register 16A 1. Register 14+Register16A→Register 16B, Reg 16B+Memory 40→Memory 36

This results in a 350% increase in speed over the traditional method.

FIG. 4 shows a further operation that is made possible with theinvention. In this operation two ALUs 30,32 are used that allows theprogrammer to achieve a very quick calculation. As the output of ALU 32must wait for the output of ALU 30, the total time of these twooperations must be smaller than one clock cycle of microprocessor 10.Assuming a hypothetical 1 second clock cycle, and an ALU time of 0.4seconds, then the total time to perform the two ALU operations would be0.8 seconds. Such time would allow the result to be stored into memory,assuming that the data can be stored immediately. If the ALU takes 0.55seconds to perform its operation then both ALU operations would take 1.1seconds which is too slow for microprocessor 10 whose hypothetical clockruns at 1 second. Thus the total operation would take 2 seconds tocomplete as 2 clock cycles are required. To overcome this probleminternal clock 12 could be slowed to a hypothetical 1.2 seconds. As thetwo ALU operations are completed within 1.1 seconds then the completecalculation is completed within 1.2 seconds (1 clock cycle) and thusthere would be a saving of a hypothetical 0.8 seconds from the previous2 seconds taken by the previous example. The internal clock 12 can beslowed by hardware or software solutions. In software, an instructioncan be sent to internal clock 12 to slow down. In hardware, circuitelements can be used to sense the need to slow down the clock in orderto perform the operation.

In FIG. 3 there is shown a diagram of the loading procedures for acomputer (not shown) which includes microprocessor 10 of the invention.The loading procedures are as follows:—

Critical procedure 100: When a computer starts up it must initiate a fewbasic or “bootstrap” operations so that it knows where to start loadingthe operating system for example. Therefore this critical procedure 100is loaded when the computer is turned on and loads the main set ofinstructions 102 together with the operating system. These criticalinstructions would be few in number and very simple so that they wouldnot need to be changed in the future.

Main set of instructions 102: The main set of instructions 102 are thebasic set of instructions which are critical in the start-up procedure.They would normally be written by the operating system programmer to beused for the operating system essential instructions. The operatingsystem instructions would be required to operate the operating system,for example a windows based operating system.

Program instructions 104,106: Each program, if it requires, can have itsown set of instructions, and therefore can be as many sets of programinstructions as long as there is sufficient memory.

FIG. 3 shows the critical procedures 100 which would be used to start upthe computer and load the operating system 102 which would load its ownset of instructions. Programs 104,106 would have their own set ofinstructions, if required. All the different programs can use eachothers' instructions, if required.

Software compilers could be developed so as to create an optimal set ofinstructions for a particular program so that it minimises memory spacerequired and maximises speed and performance. Therefore a modestprogrammer could continue to write programs in languages such as C++,Visual Basic and many other languages. The programmer would not need toworry about developing the instruction set because the compiler developsthe optimal set. The flexibility of microprocessor 10 enables a softwaredeveloper to have full control over the computer while not increasingthe computer in complexity. Microprocessor 10 can have differentprograms working on a different set of instruction sets while also beingable to implement a basic set of instructions. Microprocessor 10 is alsocapable of deleting and adding new instructions as they are needed.

The use of microprocessor 10 in a computer system allows a softwaredeveloper to have full control of what he or she wants the computer toperform. The software developer can write his or her own instruction setand then to use that instruction set in their software. This enables thesoftware developer full control over the microprocessor and thecomputer. Microprocessor 10 can also simulate other microprocessors andthe hardware level rather than at software level which is difficult andineffective. If a programmer encountered a fundamental problem eg theY2K problem he or she could simply re-write the instruction set tocalculate dates and store dates in an improved way.

In the embodiments shown in FIGS. 8 and 9 the same numerals have beenused, where applicable, to indicate similar integers to those used inFIGS. 1 to 7 to avoid repetition of description.

In FIG. 8 there is shown a similar arrangement to that shown in FIG. 1but the positions of some components have been changed. Such changesallow for the flexibility of the invention. The switch nodes A1, A2, B1,B2 etc each have N switches, where N is the bus size, eg for a 8parallel bus N=8. FIG. 8 illustrates a single grid where data can onlytravel in the X or Y directions but this can be extended to multiplegrids as shown in FIG. 9.

FIG. 9 includes a first grid 98 which corresponds to FIG. 8. A secondgrid 100 is linked to first grid 98 by nodes Z1 and Z2. The exact numberand linking of the Z nodes can vary to suit requirements. In theembodiment shown, node Z1 links node C1 of first grid 98 to node C1 ofsecond grid 100 and node Z2 links node C4 of first grid 98 to node A1 ofsecond grid 100. As each connection is made in the architecture thenumber of switching units (or nodes) required will increase and also thecomplexity of programming will also increase. The advantage of thismethod is that you can have two processors operating independently ofeach other but can also communicate with each other. It is not necessaryto have every node in grid 98 connecting to a corresponding node in grid100. There is also no limit to the number of grids 98,100 that can beconnected. Although grids 98,100 are identical in the embodiment shownthis is not necessary and variations can occur to suit requirements.There may be one instruction set decoder 34 as shown to control bothgrids 98,100 or there could be a dedicated one instruction set decoderfor each grid 98,100. Each grid 98,100 would require communication toeach other via a separate data bus or via control signals. For examplethis would enable one grid to communicate to the next grid and requestinformation or a function.

Although the preferred embodiments have shown limited components theinvention can have any number of registers, ALUs, internal memory andexternal memory of any size. Any component (ALU, register internal orexternal memory) can be connected together in many combinations and morethan one connection can take place in one clock cycle. In the preferredembodiment the registers 14-28 are shown on the Y bus but they can be onthe X bus or in any combinations on either bus. The buses can either beserial or parallel. Parallel bus will be quicker but to create a serialbus ie B=1 would be much easier as only one switch would be required pernode unlike N switches for an N-bit bus.

The invention will be understood to embrace many further modificationsas will be readily apparent to persons skilled in the art and which willbe deemed to reside within the broad scope and ambit of the invention,there having been set forth herein only the broad nature of theinvention and certain specific embodiments by way of example.

1. A microprocessor having a plurality of components which are selectedfrom registers, arithmetic logic units, memory, input/output circuitsand other similar components commonly found in microprocessors, wherebysaid plurality of components are interconnected in a manner which allowsconnection between some of the components to be varied under programcontrol.
 2. The microprocessor as claimed in claim 1, wherein saidplurality of components are interconnected on a grid whereby each ofsaid plurality of components can be switched under program control to beconnected to a predetermined selection of one or more of said pluralityof components.
 3. The microprocessor as claimed in claim 2, furtherincluding a grid connector which provides logic for interconnecting apredetermined one or more of said plurality of components with one ormore components of said plurality of components on said grid.
 4. Themicroprocessor as claimed in claim 1, wherein said plurality ofcomponents are interconnected on a grid whereby each of said pluralityof components can be switched under program control to be connected to apredetermined selection of one or more of said plurality of components,an instruction set decoder for interpreting the instruction set of saidmicroprocessor into timed signals to said components, a clock for timingoperations of said microprocessor and a grid connector which provideslogic for interconnecting a predetermined one or more of said pluralityof components with one or more components of said plurality ofcomponents on said grid.
 5. The microprocessor as claimed in claim 2,further including at least one further grid of a plurality of furthercomponents which are selected from registers, arithmetic logic units,memory, input/output circuits and other similar components commonlyfound in microprocessors, said at least one further grid of a pluralityof further components whereby at least a part of said grid is coupled toat least a part of said at least one further grid.